Fig. 4: Concentration-dependent reaction kinetics and morphological transformations of Ag NSs.

Statistical normalized scattering intensity variations of Ag NSs over time when oxidating in 10 mM Fe(NO₃)₃ solution (a) and in 50 µM FeCl₃ solution (b). The thick lines in the middle corresponds to the median intensities, and the top and bottom thin lines correspond to the first and third quartiles of the intensities. When FeCl₃ concentration is low, Ag⁺ do not precipitate on the surface of Ag NPs (c). However, as the FeCl₃ concentration increases, AgCl starts to precipitate and adhere to particle surfaces (e), altering the mass transfer dynamics around the particles and intensifying the reaction’s anisotropy (d). f Apparent reaction rate profile as a function of FeCl₃ concentration. The thick line in the middle corresponds to the median apparent reaction rate, and the top and bottom two thin lines correspond to the first and third quartiles of the apparent reaction rate. g Mean blinking times curve of the particles with blinking behavior during the oxidation process versus with the concentration of FeCl₃ solutions. h Proportion curve of particles with blinking behavior during the oxidation process versus with the concentration of FeCl₃ solutions. To extract the critical concentration and better study the transformation of reaction kinetics, the experimental data in (g, h) are fitted with a sigmoid function. Based on the fitting results, three concentration intervals with distinct reaction kinetics were identified: I, isotropic dissolution stage; II, transition stage; III, anisotropic oxidation stage. i SEM image of Ag NSs after reacting in 1 mM FeCl₃ solution. Ag NSs reaction mechanisms when reacting in low (j) and high (k) concentration FeCl₃ solutions.